We can help you with static, strength, fatigue life, and damage tolerance calculations. Our team of stress analysts can prepare strength certification reports for your product. DTB has extensive experience in finite element modeling FEM for all types of structures, including static, dynamic, modal, and random vibration PSD analyses.
Analysis of Structural Member Systems
These analyses are often used for comparison to strain gage measurements during structural tests. DTB can use your solid models,. We have experience with variable contact, non-linear materials, and non-linear analytical ultimate strength modeling. Using FEA techniques, our structural engineers can help you reduce development time - while accelerating the design process. Modeling through Autodesk Inventor and FEA using ANSYS, our experienced engineers and structural analysts can verify the findings against empirical test data, simplified models, and classical calculations to ensure accuracy.
We can verify the findings in simulated settings in our extensive test facilities to ensure product compliance. Validation and correlation of the simulation with actual experimental measurements is determined by using the displacements from string pods, as well as the load measurements from load cells. Additionally, our design team can provide services with regards to conceptual design, 3D solid modeling, assembly modeling, and detailing and drafting for both on-site and off-site development. DTB has conducted many structural test and analysis programs that involve damage tolerance principles and design.
Crack growth coupon tests are used to determine the effects of the loading frequency and environment on crack growth parameters. We can measure the crack growth rate of arresting gear during life extension tests and then correlate the actual test results to analytical predictions of damage tolerance. This type of hybrid testing and engineering work is a DTB hallmark. In conjunction with our stress analysis programs, we have experience in conducting damage tolerance analyses on aircraft antenna installations and equipment modifications. Our vibration analysts can determine stress points in your equipment and structures.
We can also predict failures and recommend preventive measures and design improvements, as required. The use of vibration analysis and FEA techniques to evaluate the dynamic characteristics of machines and structures prior to fabrication is also important.
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- ANALYSIS OF STRUCTURAL MEMBER SYSTEMS.
Simulated FEA models are used to approximate stress stiffening effects in rotating mechanical components. The FEA analysis models are used to approximate the natural frequencies and mode shapes of complex structural-mechanical systems. FEA techniques can also model the response of your equipment or structure to dynamic loads. We take pride in our ability to develop models that are only as complex as necessary in order to resolve the problem in a timely manner. DTB can analyze your product, develop a loading spectrum, and perform fatigue life predictions using strain life, stress life, or load life methods.
The strain information can be derived from test data or from finite element modeling FEM predictions.
The binormal vector is normal to both and and therefore is normal to the osculating plane. Note that a can be positive or negative whereas K is always positive, according to our definition. The torsion is zero for a plane curve since the osculating plane coincides with the plane of the curve and b is constant. We have developed expressions for the rate of change of the tangent and binormal vectors.
To complete the discussion, we consider the rate of change of the principal normal vector with respect to arc length. From ,. We use the orthogonal unit vectors I, , b to define the local reference frame for a member element. This is discussed in the following sections. The Frenet. The reference frame associated with , and b at a point, say P, on a curve is uniquely defined once the curve is specified, that is, it is a property of the.
We refer to this frame as the natural frame at P. The components b are actually the direction cosines for the natural of the unit vectors frame with respect to the basic cartesian frame which is defined by the orthogonal unit vectors 1k, 12, We write the relations between the unit vectors as ft n 12 Since 1, b are mutually or13 the direction cosines are related by thogonal unit vectors as well as 1jm6m.
Now, we consider the curve to be the reference axis for a member clement and take the positive tangent direction and two orthogonal directions in the normal plane as the directions for the local member frame. We denote the directions of the local frame by Y1, Y2, 1'3 and the corresponding unit vectors by t1, 2,. This notation is shown in Fig.
When the centroid of the normal cross-section coincides with the origin of the local frame point P in Fig. It is convenient, in this case, to take Y2, Y3 as the principal inertia directions for the cross section. In general, we can specify the orientation of the local frame with respect to the natural frame in terms of the angle between the principal normal direction and the I'2 direction.
Combining and and denoting the product of the two direction cosine matrices by the relation between the unit vectors for the local and basic. Note that the elements of fi are the direction cosines for the local frame with respect to the basic frame.
We will utilize in the next Since both frames are orthogonal, J1 chapter to establish the transformation law for the components of a vector. The curve through point Q corresponding to increasing Yj with Y2 and y3 held constant is called the parametric curve or line for yj.
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In general, there are three parametric curves through a point. We define as the unit tangent vector for the parametric curve through Q. By definition, Ui. This notation is illustrated in Fig. One can consider the vectors to define a local reference frame at Q. However, we can reduce it to an orthogonal. HAY, U. STRUm, D. If 0, the curve lies in the plane.
Then,r Oandb i3. The sign of b will depend on the relative orientation of with respect to 1.
Equation a corresponds to taking x1 as the parameter for the curve. Let 9 be the angle between and. Express t, h,! This approximation leads to sin 0 cos 0. Determine 1, n for both parametric representations. Take x1 as the parameter for b. Does y have any geometrical significance? Show that dx,. Determine D for Prob.
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Determine JI for Prob. Specialize for the case where the reference axis is in the X1 X2 plane. We express the differentiation formulas for Show that a is, in general, skewsymmetric for an orthogonal system of unit vectors, ie. Determine a. Suppose the reference axis is a plane curve but b 0. The member is not planar in this case. Suppose we know the scalar components of a vector with respect to a reference frame and we want to determine the components of the vector corresponding to a second reference frame.
We can visualize the determination of the second set of components from the point of view of applying a transformation to the column matrix of initial components. We refer to this transformation as a rotation transformation. Also, we call the matrix which defines the transformation a rotation matrix. See Fig.
We will generally use a superscript to indicate the reference frame for directions, unit vectors, and scalar. To proceed further, we must relate the two reference frames. We write, the relations between the unit vectors as. Substituting for and equating the coefficients of i' leads to. For example, R'2 is the rotation transformation matrix corresponding to a change from frame 1 to frame 2. We see that the transformation matrix for the scalar components of a vector is the inverse transpose of the transformation matrix governing the unit vectors for the reference frames.
Example 5i We consider the two-dimensional case shown in Fig. When both frames are orthogonal, the change in reference frames can be visualized as a rigid body rotation of one frame into the other, f3jk is the direction cosine for with respect to and the rotation transformation matrix is an orthogonal matrix: case of two 1 R'2 LI'jki.
Analysis of structural member systems - Jerome J. Connor - Google книги
In Sec. This frame, in turn, was defined with respect to a fixed cartesian frame 12, The equilibrium analysis of a member element involves the determination of the internal force and moment vectors at a cross section due to external forces and moments acting on the member. We shall refer to both forces and moments as "forces.
The relationship between the external force. Consider a force F and moment M acting at P shown in Fig.
The statically equivalent force and moment at Q are Feqrnv. We will write 58 in matrix form and treat force transformations as matrix transformations. We develop first the matrix transformation associated with the moment of a force about a point. Let be a force vector acting at point P and MQ the moment vector at point Q corresponding to We will always indicate the point of application of a force or moment vector with a subscript.