Patent Application
20230417625
The present disclosure is generally directed to long-duration high-G shock testing machines, and more particularly to low-cost fast set-up and reusable testing machines and methods capable of imposing high accelerations and decelerations that are sustained over relatively long durations of over 2-3 msec. Such machine would provide the means for testing ordnance and commercial products/components under high-G shock loading.
Gun-fired munitions, mortars and rail-gun munitions are subjected to high-G (setback and set-forward) acceleration during launch and target impact. Rockets are generally subjected to lower G accelerations but for significantly longer durations. High-G accelerations are also experienced during impact in munitions and in many other devices during their planned operation. Similar but more complex combinations of axial as well as lateral and bending shock loadings are experienced by air dropped weapons as they impact the target, particularly when the weapon is rocket assisted to achieve high impact velocities and when the target structure is highly heterogeneous, such as reinforced concrete or soil with large rock content. As a result, all components of the system and the system itself must survive such shock loading events and be qualified to such severe environments. High-G loading is also experienced by almost all objects during accidental drop or other similar accidental events.
Component qualification testing cannot obviously be done in an actual environment on complete assemblies. In addition to prohibitive cost involved, testing of components in actual environments would not provide the required information for determining the required component and system design margins. For these reasons, laboratory simulations of the shock loading environments are highly desirable for testing individual components, subassemblies and sometimes the complete system assembly.
In the current state of the art, shock loading environments are simulated in the industry by one of the following methods:
This method can accurately produce a desired shock response spectrum (SRS) within closely specified tolerances, but amplitude and frequency limitations of the equipment greatly restrict its applicability.
2. Live Ordnance with System Structure.
Since the actual system structure and live ordnance are used, this method has the potential to produce a shock virtually identical to the expected field environment. The cost of the test structure, however, is usually prohibitive, unless large numbers of identical tests are to be conducted. The use of live ordnance may have a wide repeatability tolerance, and does not easily allow the test levels to be increased so that an adequate design margin can be assured. For the case of gun-fired munitions, mortars and the like, the added problem is the “soft” recovery of the launched round to examine the state of the components being tested. In certain case, telemetry of data may be used to transmit back data related to the operation of certain components. However, in most cases it is highly desirable to examine the state of the components post firing. In addition, in many cases it is extremely difficult if not impossible to measure/determine the effect of shock loading on many components for transmission to a ground station via telemetry.
3. Live Ordnance with Mock Structure.
This method has most of the same features as the method “2” above, except that some cost savings are attributed to the use of a mass mock-up structure. These savings may be negated by the need for some trial-and-error testing to attain the desired component input, where geometric similarity was used in method “2” above to attain the same result. This method also suffers from the same shortcomings for testing components of gun-fired munitions and mortars and the like as indicated for the above method “2”.
4. Live Ordnance with Resonant Fixture.
This method further reduces test cost, and is a candidate for general purpose testing, due to the use of a generic resonant plate fixture. Since live ordnance is used, all the very high frequencies associated with near-field pyrotechnic shock events are produced with this method. However, a great amount of trial-and-error testing may be required to obtain the desired component input.
5. Mechanical Impact with Mock Structure.
Mechanical impacts do not produce the very high frequencies associated with the stress pulse in the immediate vicinity of a pyrotechnic device. However, most components in a typical system are isolated by enough intermediary structure such that the shock at the component location is not dominated by these very high frequencies. Instead, the shock at the component is dominated by the structural response to the pyrotechnic device, and has dominant frequencies which are typically less than 10 KHz. For these components, a mechanical impact (e.g., using a projectile or pendulum hammer) can produce a good simulation of the pyrotechnic shock environment. Test amplitudes can easily be increased or decreased by simply increasing or decreasing the impact speed. The shock level and duration can be controlled to some extent by the use of various pads affixed at the point of impact. According to this method, attempt is made to subject the structure containing the test components the impact induced acceleration (shock) profile, which close to that experienced when assembled in the actual system. The test conditions are experimentally adjusted to achieve an approximation of the actual acceleration (shock) profile. In general, a large amount of trial-and-error runs have to be made to achieve an acceptable acceleration (shock) profile. The characteristics and response of the various pads used at the impact point to increase the duration of the shock (acceleration) event is generally highly variable and dependent on temperature and moisture. In addition, due to inherent design of such mechanical impact machines and the limitations on the thickness of the pads that can be used at the impact point, high G acceleration peaks with long enough duration similar to those, e.g., experienced by munitions fired large caliber guns or mortars, cannot be achieved. For example, to achieve a peak shock acceleration level of 5000 G with a duration of 4 milliseconds, the said pad deformation has to be well over 0.6 meters (considering a reasonable ramp-up and ramp-down of 0.1 meters each), which is highly impractical. It is also appreciated by those skilled in the art that for simulating firing (setback) acceleration for most gun-fired munitions and mortars, the peak acceleration levels can generally be well over the considered 5000 Gs with significantly longer durations. It can therefore be concluded that the described mechanical impact machines do not accurately duplicate the shock profile experienced by munitions during firing or target impact and are not suitable for accurate shock testing of components to be used in such munitions.
6. Mechanical Impact with Resonant Fixture.
In this method, a resonant fixture (typically a flat plate) is used instead of a mock structure. This significantly reduces cost, and allows for general purpose testing since the fixturing is not associated with a particular structural system. The mechanical impact excites the fixture into resonance which provides the desired input to a test component mounted on the fixture. Historically, test parameters such as plate geometry, component location, impact location and impact speed have been determined in a trial-and-error fashion. In general, this method produces a simulated environment which has its energy concentrated in a relatively narrow frequency bandwidth. It should be noted here that a suitable resonant fixture for use in this method may also be a bar impacted either at the end or at some point along the length of the bar. This method is suitable for many applications in which the components are subjected to relatively long term vibration such as those induced by the system structure. The method is, however, not suitable for testing components of gun-fired munitions and the like since in such cases the munitions is subjected primarily to a single very high G setback or impact shock with relatively long duration.
In this method, the components to be tested are usually mounted in a “piston” like housing with appropriate geometry. In one method, the said “piston” is then accelerated by the sudden release of pressurized air or accelerated by the rupture of a diaphragm behind which air pressure is continuously increased until the diaphragm is failed in sheared. In another type of air gun a similar air tight “piston” within which the components to be tested are securely mounted is accelerated over a certain length of a tube by pressurized gasses. The “piston” is thereby accelerated at relatively slower rates and once it has gained a prescribed velocity, the “piston” existing the tube and impacts decelerating pads of proper characteristics such as aluminum honeycomb structures to achieve the desired deceleration amplitude and duration. The components are assembled inside the “piston” such that the said deceleration profile to correspond to the desired actual shock (acceleration) profile. In general, similar to the above method 5, air guns can be used to subject the test components to high G shock (acceleration) levels of over 30,000 Gs but for durations that are significantly lower than those experienced by gun-fired munitions, mortars and the like. It can therefore be concluded that the described mechanical impact machines do not accurately duplicate the shock profile experienced by munitions during firing or target impact and are not suitable for accurate shock testing of components to be used in such munitions.
Rocket sled is a test platform that slides along a set of rails, propelled by rockets. As its name implies, a rocket sled does not use wheels. Instead, it has sliding pads, called “slippers”, which are curved around the head of the rails to prevent the sled from flying off the track. The rail cross-section profile is usually that of a Vignoles rail, commonly used for railroads. Rocket sleds are used extensively aerospace applications to accelerate equipment considered too experimental (hazardous) for testing directly in piloted aircraft. The equipment to be tested under high acceleration or high airspeed conditions are installed along with appropriate instrumentation, data recording and telemetry equipment on the sled. The sled is then accelerated according to the experiment's design requirements for data collection along a length of isolated, precisely level, and straight test track. This system is not suitable for testing components for gun-fired munitions and mortars and the like since it can produce only around 100-200 Gs.
In this system, the components to be tested are packaged inside a round, which is fired by an actual gun (in the current system located at the U.S. Army Armament Research, Development and Engineering Center (ARDEC) in New Jersey, with a 155 mm round being fired by a 155 mm Howitzer weapon with a M199 gun tube and 540 feet of catch tubes). The projectile is then recovered using a “Soft Recovery” system. The soft catch component of the system uses both pressurized air and water to help slow down the projectile. The first part of the chain of catch tubes only contains atmospheric air. The next section, 320 feet of the tubes, contains pressurized air, followed by an 80 feet section that is filled with water. A small burst diaphragm seals one end of the pressurized air and a piston seals the other end. The piston also separates the water and pressurized air sections. The burst diaphragm and piston are replaced after each test fire. Once fired, the projectile achieves free flight for approximately 6 feet and travels down the catch tubes, generating shockwaves that interact with the atmospheric air section, the burst diaphragm, the pressurized air section, the piston, and the water section. The air section is compressed and pushed forward and shock and pressure cause the piston move against the water, all while slowing the projectile to a stop. Then the piston is ejected out of the end of the system, followed by the air and water, and finally the projectile comes to rest in a mechanized brake system. On-board-recorders inside the projectile measure the accelerations of the projectile from the gun-launch and the catch events. This system is currently provides the means to subject the test components to as realistic firing shock loading conditions as possible and provide the means to retrieve the round to examine the tested components. The cost of each testing is, however, very high, thereby making it impractical for use for engineering development. The system is also impractical for use for most reliability testing in which hundreds and sometimes thousands of samples have to be tested and individually instrumented. It also takes hours to perform each test.
The methods 1-6 described above are more fully explained in the following references: Daniel R. Raichel, “Current Methods of Simulating Pyrotechnic Shock”, Pasadena, Calif.: Jet Propulsion Laboratory, California Institute of Technology, Jul. 29, 1991; Monty Bai, and Wesley Thatcher, “High G Pyrotechnic Shock Simulation Using Metal-to-Metal Impact”, The Shock and Vibration Bulletin, Bulletin 49, Part 1, Washington D.C.: The Shock and Vibration Information Center, September, 1979; Neil T. Davie, “The Controlled Response of Resonating Fixtures Used to Simulate Pyroshock Environments”, The Shock and Vibration Bulletin, Bulletin 56, Part 3, Washington D.C.: The Shock and Vibration Information Center, Naval Research Laboratory, August 1986; Neil T. Davie, “Pyrotechnic Shock Simulation Using the Controlled Response of a Resonating Bar Fixture”, Proceedings of the Institute of Environmental Sciences 31st Annual Technical Meeting, 1985; “The Shock and Vibration Handbook”, Second Edition, page 1-14, Edited by C. M. Harris and C. E. Crede, New York: McGraw-Hill Book Co., 1976; Henry N. Luhrs, “Pyroshock Testing—Past and Future”, Proceedings of the Institute of Environmental Sciences 27th Annual Technical Meeting, 1981.
The aforementioned currently available methods and systems for testing components to be used in systems that subject them to acceleration (shock) events have a number of shortcomings for use to simulate high G acceleration (shock) events with relatively long duration, such as those encountered in large caliber guns and mortars, for example, to simulate gun-firing events with setback accelerations of over 3000 G-5,000 Gs and durations of around 5-10 milliseconds. Firstly, most of the available methods and devices, except those that are based on actual firing of the projectile from the actual gun or mortar or the like, cannot provide long enough acceleration pulse duration. Secondly, those methods that are based on actual firing of the projectile from the actual gun or mortar or the like have prohibitive cost, thereby making them impractical for engineering development tasks which requires countless iterations to achieve the desired results for individual components as well as for their assemblies. In addition, reliability tests for munitions components required testing of a very large number of components, which would make the total cost of munitions development prohibitive. Thirdly, in many component tests, it is highly desirable to instrument each component so that its behavior during the total shock environment can be monitored. Such instrumentation and monitoring is very difficult to achieve when the components to be tested have to be assembled in a rather small volume of fired projectiles.
Developing a controllable test method and predictive capability to apply this environment in testing is critical to the development of fuze, energetic, and other weapon technologies and for the development of products that can survive accidental drops or impact due to transportation vibration and the like. In munitions and other similar systems, to subject the device or system to the required acceleration events typically requires ballistic or operational testing. Both testing methods are extremely costly, personnel intensive, and introduce both technical and safety risks.
The vast majority of aircraft and satellite components, whether military or commercial, must be tested under certain shock loading conditions. That is, aircraft components must be shock tested to ensure that their design will survive its intended environment. Consequently, different aircraft components may have widely varying shock testing requirements. Currently, there is no one shock testing apparatus that can shock test aircraft components to accommodate the varying shock testing requirements for aircraft components, if at all. Thus, the industry resorts to building specialized shock testing machines or using computer simulation for shock testing, methods which are expensive and/or inaccurate.
In addition to rigorous vibration profiles, many consumer electronic components must be shock tested to determine how they will perform under certain shock conditions. Electronic components are often shock tested to determine how they will survive under unintended conditions, such as repetitive dropping. Of such consumer electronic components, device casings and circuit boards are often shock tested to determine survivability due abuse while other electronic devices are designed for heavy duty usage, such as in the construction trade and must be shock tested to determine if they are fit for their particular harsh environment. The current shock testing methods for consumer electronic devices have the same shortcomings as those described above regarding commercial aircraft. Current shock testing machines in the consumer electronics area are either very simple drop testing from heights or pneumatic shock machines, both of which are inaccurate, and their repeatability is unreliable.
Automobile components (as well as light and heavy-duty truck components) must also undergo rigorous shock testing under normal use as well as components which can fail during a crash. Some automobile components must undergo shock testing to determine how they will perform under normal conditions, such as some structural frame components while other components must undergo shock testing to determine their performance during a crash, such as electronic components, steering wheels, airbags and the like. Like other shock testing machinery currently available in the areas of commercial aircraft and consumer electronics, the shock testing of automobile components is inaccurate, their repeatability is unreliable, and they can also be relatively expensive.
In addition, currently available high-G shock loading machines, even those applying relatively low accelerations levels in the range of, for example 10 G-500 G, are not capable of applying the acceleration over relatively long durations, for example 500 G over 10 milliseconds.
The basic design of a mechanical shock testing machine 10 of prior art that uses the aforementioned method “6” is shown in the schematic of
The components to be tested 15 are attached fixedly to the mass element 11, usually via a fixture 16. In the mechanical shock machine 10, the mass element 11 acts as a “hammer” that is designed to impact an anvil 17,
To perform shock testing of the components 15, the mass element 11 (“hammer” element) is accelerated downwards in the direction of the arrow 20 towards the anvil 17. The present shock testing machines are usually installed vertically. In which case and when relatively low impact shock (deceleration) levels or very short shock durations are desired, the mass element 11 is accelerated in the direction of the arrow 20 under the gravitational acceleration, with the height of travel determining the level of velocity attained by the mass element (“hammer”) at the time of impacting the anvil 17. In other mechanical shock testing machines, particularly when higher mass element 11 velocity at impact velocity is desired, other means such as pre-tensioned bungee cords or pneumatic cylinders (not shown) are also used to significantly increase downward acceleration of the mass element 11 (in the direction of the arrow 2), thereby significantly increasing the impact speed between the mass element 11 (the “hammer” element) and the anvil 17. In those cases in which the mechanical shock testing machine 10 is installed horizontally (not shown), the mass element 11 is accelerated in the direction of the arrow 20 by the aforementioned pre-tensioned bungee cords or pneumatic cylinders or even linear motors.
The shock (deceleration) level experienced by the mass element 11 and thereby the test components 15 and its duration can be controlled to some extent by the use of various pads 21 affixed at the point of impact, i.e., between the anvil 17 surface and the impacting tip 19 of the impact element 18 of the mass element 11 (“hammer”). The shock (deceleration pulse) amplitude is also increased or decreased by simply increasing or decreasing the impact speed. The test conditions are experimentally adjusted to achieve as close approximation of the actual acceleration (shock) profile as possible.
It is therefore an object to develop a low-cost, reusable testing method and accompanying experimental and simulation capabilities that can reproduce acceleration/time profiles representative of munitions firing, weapon target penetration as well as shock loading experienced by various weapon systems and commercial products. This includes the experienced acceleration amplitude for a duration.
It is also appreciated that it is critical that the shock testing system be scalable so that they would enable testing of both small and larger devices and systems. In this regard, the shock testing system can test articles ranging from circuit boards for consumer electronics weighing several ounces to ordnances/components weighing several pounds.
A need therefore exists for the development of novel methods and resulting testing apparatus (shock testing machines) for testing components of gun-fired munitions, mortars and other devices and systems that are subjected high G acceleration (shock loading) with a relatively long duration such as projectiles fired by large caliber guns, mortars and the like. The developed methods should not be based on the use of the actual or similar platforms, for example, firing projectiles carrying the test components with similar guns such as the described in the method “9” above, due to the cost and difficulty in providing full instrumentation which would allow testing of a few components at a time, thereby making the cost of engineering development of such components and their reliability testing which requires testing of a large number of samples prohibitively high.
A need therefore exists for the development of novel methods and resulting testing apparatus (shock testing machines) for testing components of munitions such as rockets and other devices and systems that are subjected relatively low G acceleration (shock loading in tens of G rather than hundreds and thousands in the case of gun-fired munitions and mortars and those experienced during impact and the like) with relatively long duration. The developed methods should not be based on the use of the actual or similar platforms, for example, firing rockets carrying the test components, due to the cost and difficulty in providing full instrumentation which would allow testing of a few components at a time, thereby making the cost of engineering development of such components and their reliability testing which requires testing of a large number of samples prohibitively high.
A need also exists for novel mechanical shock testing machines that can provide the means of testing a large number of fully instrumented components in a relatively short time. This requires that the said mechanical shock testing machine allows rapid mounting of test components onto the test platform while allowing relatively free access to the said components, unlike the “piston” platforms used in air guns (aforementioned method “7”) or inside projectiles that are gun-launched (aforementioned method “9”).
The novel mechanical sock testing must also provide highly predictable and repeatable shock loading (acceleration) provide for testing the intended components so that the results can be used for detailed analytical model validation and tuning; for predicting the performance of the components in actual applications; and for providing the required information for the configuration of the said components and optimization of the developed configurations.
Herein is described a novel method for the configuration of shock testing machines and the resulting shock testing machines that can subject test components and systems to long duration high G acceleration pulse (shock) events. The resulting shock testing machines are shown to address the aforementioned needs and are particularly suitable for engineering development and testing of components to be used in gun-fired munitions, mortars and the like. The method is also shown to be capable of providing a configuration of shock loading machines for a wide range of accelerations and its duration.
Accordingly, shock testing machine are provided that can impart relatively long duration acceleration with a wide range of magnitudes on objects being tested. The shock testing machine provide the means of rapidly mounting and dismounting objects to be tested on the machine platform and resetting the machine for the next test. The acceleration (shock loading) level to be achieved is readily adjusted and measured via adjusting and measuring the braking force that will be provided during the testing.
These and other features, aspects, and advantages of the apparatus of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:
An isometric view of a first mechanical shock testing machine embodiment 30 is shown in
During shock loading test to be described later, the carriage member 36 is accelerated to a desired velocity from its right-most position in the direction of the arrow 39 as shown in
As can be seen in the cross-sectional view of
As can be seen in the cross-sectional view of
In general, the brake pads 48 are fixedly attached to the surface 52 and the bottom surface of the pressure plate 49 using commonly used adhesives. Stops (not shown for the sake of clarity) are also provided on the side 53 of the carriage member 36 and the side 54 of the pressure plate to prevent the brake pads 48 that are positioned between the strip members 46 from sliding out as the strip members are pulled (to the left as viewed in
To perform shock testing, the components 45 to be tested are fixedly attached to the test platform 41,
The carriage member 36 is then accelerated to a desired velocity from its right-most position in the direction of the arrow 39 as shown in
The level of the force that accelerates the carriage member 36 and its duration are selected to achieve the desired carriage member velocity as the side 56 of the carriage member reaches the stop 57.
Now as the carriage member 36 comes to a stop against the stop 57, the kinetic energy stored in the test platform 41, the braking strip members 46, and the attached components 45 that are being tested (hereinafter referred to as just the test platform) would continue to move in the direction of the arrow 39,
It is appreciated that if the initial velocity of the test platform 41 as the carriage member 36 comes to a stop and the friction force begins to act on it is V0; the total mass of the test platform 41 (including those relatively small masses of the braking strip members 46 and the attached components 45) is m; and the friction force generated by the brake pads 48 on the braking strip members 46 is Ff, then equating the initial kinetic energy of the moving mass work done by the friction force to bring the moving mass to stop yields the following expression:
(½)mV02=Ffd (1)
where d is the total distance travelled by the mass m inside the pocket 44 of the carriage member 36. Thus, the total distance d travelled by the mass m inside the pocket 44 is given by:
It is also appreciated that since the friction force Ff is essentially constant, therefore the test platform 41 (mass m) is subjected to a constant deceleration a given by:
And the duration of time t that the test platform 41 (mass m) is subjected to the acceleration a, equation (3) becomes:
It is appreciated the braking mechanism described above would apply an essentially constant deceleration pulse (shock) indicated by the equation (3) to the object 45 that is being tested as described above,
With the disclosed mechanical shock testing machine embodiment 30, relatively long deceleration pulse durations can be achieved since the length of the pocket 44 (length is considered to be measured in the direction of the arrow 39,
d=0.5at2=(0.5)(500×9.8)(3×10−3)2=0.022m
which is very small. This is in contrast with the amount of deformation that impact pads element 21 of the prior art mechanical testing machines shown in
However, it is appreciated that when the required acceleration level is higher and particularly when the required acceleration duration is longer, the total distance d that the test platform 41 has to travel inside the pocket 44 becomes significant, thereby requiring a significantly longer pocket 44 (length is considered to be measured in the direction of the arrow 39,
d=0.5at2=(0.5)(1500×9.8)(10×10−3)2=0.735m
which is over 30 times longer that the above case and that would result in a very heavy carriage member. The mechanical shock loading machine embodiment 30 of
The isometric view of the modified mechanical shock loading machine embodiment 60 is shown in the isometric view of
To perform shock testing, the components 64 to be tested are fixedly attached to the test platform 61,
The carriage member 136 is then accelerated to a desired velocity from its right-most position in the direction of the arrow 39 as shown in
The level of the force that accelerated the carriage member 136 and its duration are selected to achieve the desired carriage member velocity as the side 56 of the carriage member reaches the stop 57.
Now as the carriage member 136 comes to a stop against the stop 57, the kinetic energy stored in the test platform 61, the braking strip members 46, and the attached components 64 that are being tested (hereinafter referred to as just the test platform) would continue to move in the direction of the arrow 39,
In the isometric view of the mechanical shock loading machine embodiment 60, the test platform 61 is shown to consist of a frontal portion 62 and a tail portion 63, which is configured to ride in the pocket 44 of the carriage member 136. In general, the tail portion 63 is provided so that as the carriage member 136 together with the test platform are accelerated to the aforementioned desired velocity V0 before the carriage member 136 is stopped, the test platform would undergo minimal lateral movements relative to the carriage member 136. It is therefore appreciated that the length of engagement between the tail section 63 of the test platform 61 and the pocket 44 does not have to be long to serve this purpose. It is also appreciated that when the lateral movements are not of concern, particularly for tests requiring lower velocities V0, then the tail section 63 may be eliminated.
It is appreciated that since the mechanical shock loading machine configuration of the embodiment 60 of
In the shock loading machine embodiment 60 of
In the above mechanical shock loading machine embodiments, the carriage members (136 and 36 in the embodiments 30 and 60 of
The first method of accelerating the carriage member of the mechanical shock testing machine to the desired velocity is shown in the schematic of
In the schematic of the embodiment 80 of
To perform a shock loading test, the object to be tested is fixedly attached to the test platform 71. The carriage member 65 is then released from a predetermined height, so that as it is accelerated down in the direction of the arrow 74 under gravitational acceleration, at the time that the carriage side member 75 comes to a stop against the stop member 76 (which is fixedly attached to the machine structure 70), it has gained the desired initial velocity V0, equation (4). It is appreciated that the height of travel of the carriage member 65 under the gravitational acceleration determines the initial velocity V0 as was previously indicated. In general, the carriage member 65 is held to the top support 65 at the desired height by a quick release mechanism (not shown), which is then released by the pulling of a cable or string after removing its safety lock pin. Such quick release mechanisms with safety pins are well known in the art. Once the carriage member 65 has been stopped by the stop 76, the test platform 71 together with its attached test object is decelerated by the provided friction forces acting on the at least one braking strip 73 as was described for the embodiments 30 and 60 of
A modified version of the vertical shock loading machine embodiment 80 is shown in
In the mechanical shock loading machine embodiment 85 of
As can be seen in the cut-away section of the
To perform a shock loading test, the object to be tested 83 is fixedly attached to carriage member 81,
To perform a shock loading test, the carriage member 81 is therefore released from a predetermined height, so that as it is accelerated down in the direction of the arrow 88 under gravitational acceleration, at the time that the at least one braking strip member becomes taut, it has gained the desired initial velocity V0, equation (4). It is appreciated that the height of travel of the carriage member 81 under the gravitational acceleration determines the said initial velocity V0 as was previously indicated. In general, the carriage member 81 is held to the top support 82 at the desired height by a quick release mechanism (not shown), which is then released by the pulling of a cable or string after removing its safety lock pin. Such quick release mechanisms with safety pins are well known in the art. Once the section 87 of the at least one braking strip member 71 has become taut, the carriage member 81 together with its attached test object 83 are decelerated by the provided friction forces acting on the at least one braking strip 73 as was described for the embodiments 30 and 60 of
In mechanical shock testing machines, particularly when higher acceleration shock loading and durations are required, other means such as pre-tensioned bungee cords or pneumatic or electric drives may be used to achieve significantly higher carriage member velocities, for example for the embodiments 30, 60 and 80 of
The indicated second and third methods are very similar and both involves the release of the mechanical shock loading machine carriage member after pre-tensioning at least one bungee that connects the carriage member to the (usually base) structure of the machine. The main difference between the two methods is the process of pre-tensioning the bungees. The second and methods of pre-tensioning at the at least on bungee are shown in the schematics of
The second method of accelerating the carriage member of the mechanical shock testing machine to the desired velocity is shown in the schematic of
In shock loading machines using this method of accelerating the carriage member to the desired velocity, the carriage member 89 still rides on mounted rails 90 and 91. The rails are mounted firmly in a top and a bottom supports 92 and 93, respectively. The top and bottom support members 92 and 93 are generally rigid and massive enough to provide stability and may also be fixedly attached to properly sized foundation or machine structure 94 (shown as ground).
The carriage member 89 is initially attached to the support member 92 by a quick release mechanism 95 as shown in
It is appreciated that in many cases, the winch may be attached past the support 93 to allow long enough bungee cords to be used to accelerate the carriage member 89 long enough to achieve high initial velocity V0, equation (1), before the friction mechanisms begins to decelerate the test platform (41, 62 and 71
To perform a shock loading test, the object to be tested is fixedly attached to the test platform (41, 62 and 71
The third method of accelerating the carriage member of the mechanical shock testing machine to the desired velocity is shown in the schematic of
In shock loading machines using this method of accelerating the carriage member to the desired velocity, the carriage member 100 still rides on mounted rails 101 and 102. The rails are mounted firmly in a top and a bottom supports 103 and 104, respectively. The top and bottom support members 103 and 104 are generally rigid and massive enough to provide stability and may also be fixedly attached to properly sized foundation or machine structure 105 (shown as ground).
The carriage member 100 is initially held in its “neural” position by the at least one bungee cord 106 on one end and the winch cable 107 on the other as shown in
The winch 109 is used to collect the winch cord 107, pulling the carriage member 100 towards it, thereby extending the at least one bungee cord 106 and storing mechanical potential energy in it due to its elastic deformation. It is appreciated that the winch 109 may be either operated manually by the rotation of the handle 109 or via an electric motor via a speed reduction gearing (not shown) commonly used in such winches.
To perform a shock loading test, the object to be tested is fixedly attached to the test platform (41, 62 and 71
It is appreciated that in many cases, the winch 109 and the bungees may be attached past the supports 103 and 104 to allow long enough bungee cords to be used to accelerate the carriage member 100 long enough to achieve high initial velocity V0, equation (1), before the friction mechanisms begin to decelerate the test platform (41, 62 and 71
In the above embodiments, the friction force adjustment of the friction mechanisms is shown to be achieved by pressure adjustment screws (50 in
In the above embodiments, the braking strip members (46 and 73 in
It is appreciated by those skilled in the art that as it was previously indicated, to achieve relatively high shock loading acceleration and duration for shock loading machines, such as the shock loading machine embodiments 30 and 60 of
It is appreciated that as it was previously described, for a prescribed shock loading acceleration level, the duration of the shock acceleration is increased by increasing the velocity of the test platform as the carriage member 136 is stopped by the stop 57,
In addition, since the shock loading machine embodiments 30 and 60 of
The above minimization of the mass of the test platform assembly can be achieved by the following modification of the embodiment 60 of
The isometric view of the modified mechanical shock loading machine embodiment 120 is shown in
Test platform 121 is provided with groove 122, which runs along the length of the test platform and is wide and deep enough to allow test platform 121 to freely pass over the stop 57 as it moves in the direction of the arrow 124. The stop 57 is fixedly attached to the shock loading machine structure 33 and may be provided with a shock absorber or other kinetic energy absorbing members to prevent the braking member 126 from bouncing back as it is brought to a stop as is described later.
As can be seen in the cross-sectional view of
Four pressure adjustment screws 129,
To perform shock acceleration testing, the components 123 to be tested are fixedly attached to test platform 121,
The friction force adjustment can be done as was previously described for the embodiment 30 of
The test platform 121 is then accelerated to the desired velocity as was previously described for the embodiments 30 and 60 of
The level of the force that accelerates the test platform 121 and its duration are selected to achieve the desired test platform velocity as the braking member assembly 126 engages the stop member 57.
Now as the braking member assembly 126 comes to a stop against the stop 57, the kinetic energy stored in the test platform 121, the braking strip members 46, and the attached components 123 that are being tested (also referred to as just the test platform) would continue to move in the direction of the arrow 39,
It is appreciated that as can be observed in the cross-sectional view of
However, for higher speed shock loading test, i.e., when longer duration shock loading acceleration levels are required, the surface of contact between the braking member 126 and stop member 57 can be significantly increased by mounting the braking strip members 46 as shown in the top view “G” of
It is appreciated that the modification of 90 degrees rotation of the braking member 126 and the braking strip members 46,
The braking member of the mechanical shock loading machine embodiment 120 is shown in
The mechanical shock loading machine embodiment 120 described with regard to any of
While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.
This application is a Continuation-In-Part application of U.S. patent application Ser. No. 17/555,609, filed on Dec. 20, 2021, which claims priority to U.S. Provisional Application No. 63/128,111 filed on Dec. 20, 2020, the entire contents of each of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63128111 | Dec 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17555609 | Dec 2021 | US |
| Child | 18244271 | US |
