A typical joint construction of a point-supported glass structure is shown with a cushioning material sandwiched between the fastener and the glass. The cushion layer is placed between the metal fastener and the glass plate as a buffer layer for the fastener and the glass plate, and serves to reduce the local stress at the edge of the glass hole and to tightly bond the glass and the metal fastener. At the same time, due to the large coefficient of friction between the mat and the glass, the relative slip of the mat and the glass can be prevented, and the connection between the glass sheet and the fastener is more firm. Since the metal fastener is divided into a floating head and a countersunk head, there are two types of the cushion layer as shown.
At present, the cushion layer in the point-supporting glass structure is more plastic material. The tensile modulus of the plastic material is between 0.235 GPa and the Poisson's ratio is between 0.80.49. German research data shows that the thickness of the cushion is usually between 15mm. These two methods are also the most common methods currently used to deal with contact problems.
Second, the establishment and calculation of the finite element model In the study of the influence of the cushion on the bearing capacity of the metal plate with metal fasteners, in order to eliminate the randomness of the defects of the glass and the randomness of the drilling on the strength of the glass, a circular glass is required. Board model. In order to eliminate the bending stress in the glass, a partial circular glass plate model must be used. The diameter of the glass plate is about the diameter of the hole. 59. 5. The interaction between the single floating head fastener with the cushion and the circular glass plate is analyzed. Function model: The inner shaft of the fastener is directly under the Beijing Science and Technology Commission Fund Project (953301101).
The connecting diameter of the cushioned fastener and the disc-shaped glass plate is di=240, 5Qmm, the diameter of the upper and lower jaws of the fastener is 70mm, the thickness of the pad is 5mm, the thickness of the cushion is 1.2, 2, 4mm, and the elastic modulus of the cushion The amount of Ei = 2.5, 510 GPa, the outer diameter of the glass plate is 6 = 250 mm, and the thickness of the glass plate is 5 mm. A total of 27 sets of models are calculated, and the unit concentration is added to the ends of the fasteners in each model. Due to the symmetry of each model, only a quarter model is needed. A solid end constraint is applied to the edge of the glass sheet to impart a symmetrical constraint on the cross section of the glass, mat and fastener. Fasteners, cushions, and glass panels are modeled using solid elements. Material properties: fastener (steel) elastic modulus 2.06X105N/mm2, Poisson's ratio 0.3; glass plate (plain glass) elastic modulus 0 105N/mm2, Poisson's ratio 0.2; cushion (plastic) elastic modulus 2. 103, 5.0X103, 1.0X104N/mm2 three, Poisson's ratio takes the intermediate value of plastic material 45. The fastener and the mat layer are glued.
Considering the contact between the mat and the glass plate, the surface of the soft body and the soft body are simulated by the contact unit. Since the elastic modulus of the cushion is smaller than that of the glass, the cushion layer is set as the contact surface, and the contact unit is conta174. The glass plate is set as the target surface, and the target unit is targe 170. In the process of generating the contact unit pair, considering the friction stress on the contact surface, the friction coefficient between the glass and the cushion is 0.4FP Bowden, D. Taber Author, Chen Shaozhen and other translations. Friction and lubrication of solids. Mechanical Industry Press, 1982. Corrigendum 2 (1) 1 year, 11 issues, page 58, left column, as follows, to correct the W-beam 匕 匕 70 part of the crack unfolding map W. We apologize for the inconvenience caused to our readers due to our work mistakes.
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