Dynamic Response of Adhesively Bonded Beams Subjected to Harmonic Peeling Loads

1999 ◽  
Author(s):  
H. R. Hamidzadeh ◽  
J. L. Prescher ◽  
H. Nayeb-Hashemi
Keyword(s):  
Dynamic Response ◽  
Natural Frequency ◽  
System Response ◽  
Shear Stresses ◽  
Harmonic Force ◽  
Factors Affecting ◽  
Initiation And Propagation ◽  
Stress Changes ◽  
Bonded Joint ◽  
Out Of Plane

Abstract The only viable method to join some components is by using adhesive. These components are often subjected to dynamic loading, which may cause initiation and propagation of failure in the joint. In order to insure the reliability of these structures, their dynamic response and factors affecting their response must be understood. Dynamic response of a single lap joint subjected to an out of plane harmonic force is evaluated. The bonded joint is modeled as Euler Bernoulli beams joined with an adhesive and constrained at one end and subjected to a harmonic force at the free end. The results show that the system response is not sensitive to the damping characteristic of the adhesive. In contrast, the elastic properties, and geometry of adhesive and adherends dominate the response. Significant peel and shear stresses develop in the over lap. These stresses are confined to the edge of the overlap and their magnitude increases as the frequency approaches the natural frequency of the system. The results show that the direction of the shear stress changes as the frequency of applied load sweeps over the first natural frequency. In contrast the peeling stress direction does not change as result of sweeping frequency over the first natural frequency.

Evaluation of Bond Strength With Void Subjected to Harmonic Peeling Loads

2001 ◽  
Author(s):  
A. Vaziri ◽  
H. R. Hamidzadeh ◽  
H. Nayeb-Hashemi
Keyword(s):  
Shear Stress ◽  
Dynamic Response ◽  
System Response ◽  
Harmonic Force ◽  
Adhesion Properties ◽  
High Adhesion ◽  
Initiation And Propagation ◽  
Bonded Joint ◽  
Out Of Plane ◽  
Bond Area

Abstract Joining components by using adhesives is becoming more popular with the development of adhesives with high adhesion properties. These components are often subjected to dynamic loading, which may cause initiation and propagation of failure in the joint. In order to ensure the reliability of these structures, their dynamic response and its variation with the presence of defects in the bonded area, must be understood. Dynamic response of a single lap joint subjected to an out of plane harmonic force is evaluated. The bonded joint is modeled as Euler Bernoulli beams, joined with an adhesive and constrained at one end and subjected to a harmonic force at the free end. The results show that the system response is not sensitive to a range of adhesive loss factor of 0-1. Furthermore, the system response is little affected by the presence of void in the bond area. The system response seems to be more sensitive to the void location than to its size. Peel and shear stress in bond area are obtained and found to be confined to the edge of the overlap. For adhesive and adherents properties and geometry investigated the maximum peel and shear stress in the bond area are little affected with the presence of a central void which covers less than 60% of the over lap length for all range of frequency. However, when the frequency of the applied load is close to the natural frequency of the structure, a void increases both maximum peel and shear stress.

The Effects of the Adhesively Bonded Repair Patch on the Dynamic Response of the Composite Beam Under a Harmonic Peeling Load

2003 ◽  
Author(s):  
A. Vaziri ◽  
H. Nayeb-Hashemi ◽  
M. Olia
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Dynamic Response ◽  
Composite Beam ◽  
Composite Beams ◽  
System Response ◽  
Shear Stresses ◽  
Test Technique ◽  
Coupled Equations ◽  
Bonded Repair

The dynamic response of an adhesively patched repaired composite beam under a harmonic peeling load was obtained theoretically and experimentally. In the theoretical part, dynamic responses of the repaired composite beams were obtained by modeling the parent beam as the Euler-Bernouli beam and the repaired patch as the Euler-Bernouli beam supported on a viscoelastic foundation, which resist both peeling and shear stresses. Both axial and transverse displacements were considered in deriving the coupled equations of motion. The effects of the adhesive loss factor, as well as its elastic modulus on the vibrational behavior of the repaired composite beams were investigated theoretically. In addition, finite element modal analyses were performed to justify the results of the proposed theoretical model. In the experimental part, unidirectional fiberglass reinforced epoxy composite specimens with various repaired patch length, thickness and material properties were manufactured. The patch section was either the fiberglass epoxy or E-glass fiber reinforced composites with various ply sequences. Patches were bonded to the composite beam using an epoxy. The system response was measured by the hammer test technique using a non-contact laser vibrometer. The resonant frequencies and damping ratio of the specimens were evaluated from the dynamic response of the composite beam and the results were compared to that of the theoretical and finite element analyses. The results showed that the dynamic response of the repaired composite depended on the adhesive elastic modulus. For the composite repaired with a high adhesive elastic modulus, the beam may act as a classical Euler-Bernouli composite beam. For the composite patched with a low elastic modulus adhesive, the first resonant frequency of the system may decrease up to 22%. In contrast, the natural frequencies may not significantly change having used adhesive with a high elastic modulus.

Stress concentration factors for the torsion of curved beams of arbitrary cross-section

2006 ◽  
Vol 220 (12) ◽  
pp. 1709-1726 ◽  
Author(s):  
R E Cornwell
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Cross Section ◽  
Cross Sections ◽  
Shear Stresses ◽  
Curved Beams ◽  
Finite Element Implementation ◽  
Out Of Plane ◽  
Concentration Factors ◽  
Stress Concentration Factors

There are numerous situations in machine component design in which curved beams with cross-sections of arbitrary geometry are loaded in the plane of curvature, i.e. in flexure. However, there is little guidance in the technical literature concerning how the shear stresses resulting from out-of-plane loading of these same components are effected by the component's curvature. The current literature on out-of-plane loading of curved members relates almost exclusively to the circular and rectangular cross-sections used in springs. This article extends the range of applicability of stress concentration factors for curved beams with circular and rectangular cross-sections and greatly expands the types of cross-sections for which stress concentration factors are available. Wahl's stress concentration factor for circular cross-sections, usually assumed only valid for spring indices above 3.0, is shown to be applicable for spring indices as low as 1.2. The theory applicable to the torsion of curved beams and its finite-element implementation are outlined. Results developed using the finite-element implementation agree with previously available data for circular and rectangular cross-sections while providing stress concentration factors for a wider variety of cross-section geometries and spring indices.

Free Bending Vibrations of a Centrally Bonded Symmetric Double Lap Joint (or Symmetric Double Doubler Joint) With a Gap in Mindlin Plates or Panels

2007 ◽  
Author(s):  
U. Yuceoglu ◽  
O. Gu¨vendik ◽  
V. O¨zerciyes
Keyword(s):  
Boundary Conditions ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Shear Stresses ◽  
Lap Joint ◽  
Bending Vibrations ◽  
Joint System ◽  
Adhesive Layers ◽  
Bonded Joint ◽  
Free Bending

In this present study, the “Free Bending Vibrations of a Centrally Bonded Symmetric Double Lap Joint (or Symmetric Double Doubler Joint) with a Gap in Mindlin Plates or Panels” are theoretically analyzed and are numerically solved in some detail. The “plate adherends” and the upper and lower “doubler plates” of the “Bonded Joint” system are considered as dissimilar, orthotropic “Mindlin Plates” joined through the dissimilar upper and lower very thin adhesive layers. There is a symmetrically and centrally located “Gap” between the “plate adherends” of the joint system. In the “adherends” and the “doublers” of the “Bonded Joint” assembly, the transverse shear deformations and the transverse and rotary moments of inertia are included in the analysis. The relatively very thin adhesive layers are assumed to be linearly elastic continua with transverse normal and shear stresses. The “damping effects” in the entire “Bonded Joint” system are neglected. The sets of the dynamic “Mindlin Plate” equations of the “plate adherends”, the “double doubler plates” and the thin adhesive layers are combined together with the orthotropic stress resultant-displacement expressions in a “special form”. This system of equations, after some further manipulations, is eventually reduced to a set of the “Governing System of the First Order Ordinary Differential Equations” in terms of the “state vectors” of the problem. Hence, the final set of the aforementioned “Governing Systems of Equations” together with the “Continuity Conditions” and the “Boundary conditions” facilitate the present solution procedure. This is the “Modified Transfer Matrix Method (MTMM) (with Interpolation Polynomials). The present theoretical formulation and the method of solution are applied to a typical “Bonded Symmetric Double Lap Joint (or Symmetric Double Doubler Joint) with a Gap”. The effects of the relatively stiff (or “hard”) and the relatively flexible (or “soft”) adhesive properties, on the natural frequencies and mode shapes are considered in detail. The very interesting mode shapes with their dimensionless natural frequencies are presented for various sets of boundary conditions. Also, several parametric studies of the dimensionless natural frequencies of the entire system are graphically presented. From the numerical results obtained, some important conclusions are drawn for the “Bonded Joint System” studied here.

Dynamics Analysis of Refrigeration Compressor Based on Finite Element and Experimental Modes

2012 ◽  
Vol 499 ◽  
pp. 238-242
Author(s):  
Li Zhang ◽  
Hong Wu ◽  
Yan Jue Gong ◽  
Shuo Zhang
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Modal Analysis ◽  
Natural Frequency ◽  
High Precision ◽  
3D Model ◽  
Finite Element Models ◽  
Dynamics Analysis ◽  
Response Characteristics ◽  
Dynamic Response Characteristics

Based on the 3D model of refrigeration's compressor by Pro/E software, the analyses of theoretical and experimental mode are carried out in this paper. The results show that the finite element models of compressor have high precision dynamic response characteristics and the natural frequency of the compressor, based on experimental modal analysis, can be accurately obtained, which will contribute to further dynamic designs of mechanical structures.

Vibrations of an Intermediately Supported U-Bend Tube

1975 ◽  
Vol 97 (1) ◽  
pp. 23-32 ◽  
Author(s):  
L. S. S. Lee
Keyword(s):  
Natural Frequency ◽  
Natural Frequencies ◽  
Experimental Tests ◽  
Bending Stiffness ◽  
Stiffness Ratio ◽  
Plane Vibration ◽  
Straight Beam ◽  
Out Of Plane ◽  
Straight Segments ◽  
Good Agreement

Vibrations of an intermediately supported U-bend tube fall into two independent classes as an incomplete ring of single span does, namely, the in-plane vibration and the coupled twist-bending out-of-plane vibration. Natural frequencies may be expressed in terms of a coefficient p which depends on the stiffness ratio k, the ratio of lengths of spans, and the supporting conditions. The effect of the torsional flexibility of a curved bar acts to release the bending stiffness of a straight beam and hence decrease the natural frequency. Some conclusions for an incomplete ring of single span may not be equally well applicable to the U-tube case due to the effects of intermediate supports and the presence of the supporting straight segments. Results of the analytical predictions and the experimental tests of an intermediately supported U-tube are in good agreement.

scholarly journals Research on the Resonance Characteristics of Rock under Harmonic Excitation

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Siqi Li ◽  
Shenglei Tian ◽  
Wei Li ◽  
Tie Yan ◽  
Fuqing Bi
Keyword(s):  
Resonance Frequency ◽  
Natural Frequency ◽  
Excitation Frequency ◽  
Harmonic Excitation ◽  
Theoretical Research ◽  
Transform Method ◽  
Factors Affecting ◽  
Least Action ◽  
Principle Of Least Action ◽  
Resonance Frequencies

In order to study the resonance characteristics of rock under harmonic excitation, two vibration models have been presented to estimate the natural frequency of rock encountered during the drilling. The first one is a developed single-DOF model which considers the properties and dimensions of the rock. The second one is a multi-DOF model based on the principle of least action. Subsequently, the modal characteristics, as well as the influence of excitation frequency, the mechanical properties, and dimensions of the rock on its resonance frequency, are analyzed by using FEM. Finally, the ultrasonic test on artificial sandstones and materials of drill tools are carried out indoor, and the FFT transform method is adopted to obtain their resonance frequencies. Based on the analysis undertaken, it can be concluded that the natural frequency of the rock increases with the change of vibration mode. For the same kind of rock, the resonance frequency is inversely proportional to mass, while for the different kinds of rocks, the mechanical parameters, such as density, elastic modulus, and Poisson’s ratio, determine the resonance frequency of the rock together. Besides, the shape of the rock is also one of the main factors affecting its resonance frequency. At last, the theoretical research results are further verified by ultrasonic tests.

Free and Forced Longitudinal Vibrations of a Cantilevered Bar With a Crack

1992 ◽  
Vol 114 (2) ◽  
pp. 171-177 ◽  
Author(s):  
K. R. Collins ◽  
R. H. Plaut ◽  
J. Wauer
Keyword(s):  
Steady State ◽  
Natural Frequency ◽  
Transverse Crack ◽  
Breathing Crack ◽  
Longitudinal Vibrations ◽  
Harmonic Force ◽  
Frequency Spectra ◽  
Crack Location ◽  
Fundamental Natural Frequency ◽  
Steady State Amplitude

Longitudinal vibrations of a cantilevered bar with a transverse crack are investigated. For undamped, unforced vibrations, frequency spectra are computed and the effects of the crack location and compliance on the fundamental natural frequency are determined. For vibrations caused by a distributed, longitudinal, harmonic force, the steady-state amplitude of motion of the free end is plotted as a function of the forcing frequency, crack location, and crack compliance, and frequency spectra are also obtained. Results for a breathing crack are compared to those for a crack which remains open and those for an uncracked bar.

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