• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1732-1738
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• 2003

The test specimen in environmental vibration test is connected to the fixture through several attachment points. The forces generated by the shaker must be transmitted equally to all attachment points. The forces transmitted to attachment points, however, are different because of the flexural vibration of the fixture. The variations of the transmitted force cause the under-test, especially at anti-resonance frequencies, in vibration test control. Anti-resonance frequencies at the attachment points of the fixture must be same in order to avoid the under-test in vibration test control. The structural modification of the fixture is needed so that anti-resonance frequencies at attachment points have the same value. In this paper, the method to calculate the anti-resonance frequencies and those sensitivities is presented. This sensitivity analysis is applied to the structural modification of the fixture excited at multi-points by the shaker. The antiresonance frequencies at the attachment points of the fixture can have the same value after structural modification, and the under-test in the vibration test control can be removed. Several computer simulations show that the proposed method can remove the under-tests, which are not removed in conventional vibration test control.

• 소음진동
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• 제8권1호
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• pp.180-186
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• 1998

Vibration test fixture is used in random vibration control testing. The specified reference spectrum should be transmitted equally to the specimen attachment points on the fixture. In most practical cases, however, spectrum at each of specimen attachment points may be quite different from the specified reference spectrum because of the dynamic characteristics of vibration test fixture. This paper proposes the method of experimental dynamic modification of fixture system for vibration test so that the reference spectrum can be transmitted to the specimen attachment points without distortion. The stiffness of mounts of specimen and the thickness of fixture are considered as design variables. The frequency response functions of specimen used for input data are obtained from vibration testing, and the frequency response functions of fixture are obtained from finite element modeling. The sensitivities of frequency response functions at specimen attachment points to the mount stiffness are derived from synthesis method of transfer function. And the sensitivities to the thickness of fixture are also derived from finite element modeling. The presented method is verified by computer simulation and vibration testing.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.258-262
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• 2007

Satellite launch vehicle is exposed to some dynamic environment during its flight. Particularly, the safety of launch vehicle structure is surely verified under vibration environment in low frequency range. Sine sweep test is generally performed to describe this low frequency vibration environment. Dynamic property of vibration fixture is considered to get the correct property of target object. This vibration fixture should really be an extension of the armature in the form of a very rigid structure that can transfer the required force at the required frequency. An optimum fixture would have its lower natural frequency about 50% higher than the highest required forcing frequency in order to avoid fixture resonances during the test. In this study, the vibration mode analysis considering the mass of target object to design the vibration fixture. And the modal test of vibration fixture is performed to conform the design.

• 소음진동
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• 제6권3호
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• pp.317-323
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• 1996

This paper proposes the method of experimental structural dynamic modification of fixture for environmental vibration test control. This method can predict the responses at any points on the fixture utilizing the experimental data, and structural dynamic modification of fixture is made using the predicted responses for the spectra at the specimen attachment points to meet the specified reference spectrum. From the results of controlling the fixture before and after modification by conventional control method and optimal reference spectrum, which has been previously reported by the authors, the proposed method is shown to be an effective one.

• 한국정밀공학회지
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• 제6권3호
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• pp.46-59
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• 1989

The purpose of test fixture is to mechanically couple energy from a shaker into a test specimen. And then it is necessary to design a fixture of shich the fundamental natural frequency is over than one half times as high as the highest frequency of interest. But the dynamic behavior of vibration test fixture is usually different from, often far different from, what has been calculated. In this paper, the optimal dimensionless frequency parameter, ${lambda}$'s, are calculated from the test results of a various and complex shaped fixtures.

• Journal of Advanced Marine Engineering and Technology
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• 제25권1호
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• pp.87-94
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• 2001

Filament winding process is a comparatively simple operation in which continuous reinforcements in the form of roving are wound over a rotating mandrel. And now it is well established as a versatile method for storage tanks and pipe for the chemical and other industries. In this study, tensile strength of a filament wound ring specimens were evaluated by split disk test fixture and dress disk test fixture. The results obtained from experiments were compared with the theoretical values obtained by the rule of mixture. And the purpose of this paper is to suggest an appropriate test method for the evaluation of tensile properties of filament wound structures. The tensile strength of a ring specimens tested by the dress disk test showed better agreement with the theoretical values than of a ring specimen tested by the split disk test because the stress concentration in edges of s split disk test fixture is more severe than the that of dress disk test fixture. The results showed that the tensile strength of a ring specimen was influenced by the geometry of test fixture, the continuity of fibers, fiber-tension, fiber-end and stress concentration in specimen.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 추계학술대회 논문집(Proceeding of the KOSME 2000 Autumn Annual Meeting)
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• pp.15-20
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• 2000

Filament winding process is a comparatively simple operation in which continuous reinforcements in the form of roving are wound over a rotating mandrel. And it is now well established as a versatile method for storage tanks and pipe for the chemical and other industries. In this study, tensile strength of a filament wound ring specimens were evaluated by split disk test fixture and dress disk test fixture. The results obtained from experiments were compared with the theoretical values obtained by the rule of mixtures in composites . And the purpose of this paper is the suggestion of an appropriate test method for the evaluation of tensile properties of filament wound structures. The tensile strength of a ring specimen tested by the dress disk test showed better agreement with the theoretical values than that of a ring specimen tested by the split disk test because the stress concentration in edges of a split disk test fixture is more severe than that of dress disk test fixture. The results showed that the tensile strength of a ring specimen was influenced by the geometry of test fixture, the continuity of fibers, fiber-tension, fiber-end and stress concentration in specimen.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.203-207
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• 2000

Filament Winding Process is a comparatively simple operation in which continuous reinforcements in the form of roving are wound over a rotating mandrel. And now well established as a versatile method for storage tanks and pipe for the chemical and other industries . In this study, tensile strength of a filament wound ring specimens were evaluated by split disk test fixture and dress disk test fixture , The results obtained from experiments were compared with the theoretical values obtained by the rule of mixtures. And the purpose of this paper is the suggestion of an appropriate test method for the evaluation of tensile properties of filament wound structures .The tensile strength of a ring specimen tested by the dress disk test showed better agreement with the theoretical values than of a ring specimen tested by the split disk test because the stress concentration in edges of a split disk test fixture is more severe than that of dress disk test fixture. The results showed that the tensile strength of a ring specimen was influenced by the geometry of test fixture, the continuity of fibers, fiber-tension, fiber-end and stress concentration in specimen.

• 대한치과기공학회지
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• 제35권3호
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• pp.201-207
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• 2013

Purpose: In this study, the loosening torque test was conducted with three implant products that are produced, approved and sold in Korea, which are manufactured in different fixture and abutment tightening methods (internal submerged type, internal morse taper type, and external type) to examine the loosening torque of the screw according to the method of tightening the implant fixture and abutment. Methods: In the loosening torque test, the three types of fixtures and abutments with different tightening methods were tightened by rotating them clockwise with a $30N{\cdot}cm$ force using a driver equipped with an electric torque meter. The results of the test are as follows. Results: The loosening torque values of the internal submerged type, internal morse taper type and external type implants were $24.10{\pm}0.742N{\cdot}cm$, $29.10{\pm}1.710N{\cdot}cm$, and $26.60{\times}1.636N{\cdot}cm$, respectively. Conclusion: The screw loosening torque values of the three fixture and abutment tightening methods were analyzed via Kruskal Wallis test layout, and they were significantly different (p<0.05).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1996년도 춘계학술대회논문집; 부산수산대학교, 10 May 1996
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• pp.100-105
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• 1996

This paper proposes the method of experimental structural dynamic modification of fixture for environmental vibration test control. This method can predict the responses at any points on fixture utilizing the experimental data, and structural dynamic modification of fixture is made using the predicted responses for the spectra at the speciment attachment points to meet the specified reference spectrum. From the results of controlling the fixture before and after modification by conventional control method and optimal reference spectrum, which has been previously reported by the authors, the proposed method is shown to be an effective one.