Bonded Assembly a hlawhchham em? Internal Stress tihdam dan hi hrethiam hmasa phawt ang che

Bonding joint a chhiat chuan kan hmalakna hmasa ber chu adhesive strength a tling em tih te, surface treatment a dik em tih te, impregnation a tawk em tih te, materials te chu a upa tawh em tih te tehna a ni tlangpui.

Mahse, engineering application tak takah chuan hlawhchhamna thenkhat chu commissioning atanga tan chauh a ni lo va; chu ai chuan, adhesive chu a dam kim tawh chuan hlauhawmna awm thei chu a awm tawh a ni.

He hlauhawmna awm thei hi residual internal stress awm vang a ni.

Hmuh theih loh leh direct taka teh harsa tak a ni a, chutih rualin a nihna takah chuan thuruk a ni lo. A awlsam zawngin, adhesive hian a curing leh cooling laiin shrinkage a tawk a; a chhehvel substrate chuan a free deformation a tihkhawtlai chuan a unshrinkable portion chu adhesive layer chhungah residual stress a lo ni ta a ni.

Vawiin hian he concept hi uluk taka hriatthiam theih nan ka kaihruai vek ang che u.

Internal stress hlauhawmna hi "energy-storage" nature a ni.

Curing a nih chuan adhesive layer hian elastic strain energy thenkhat a khawlkhawm thin. He energy hi a hnu lama interfacial delamination, microcrack propagation, leh warping deformation awm theihna tura underlying driving force atan a thawk a ni.

Interface delamination leh delamination te hi entirnan la ila: internal stress te chu operational load chungah a pung khawm a, chu chuan interface stress tak tak chu design-calculated rating value aiin a tam zawk daih a ni. Phên dangin sawi ila, adhesive layer-in formal service a ṭan hma pawh hian interface chu pre-tensioning nasa lutuk a tawk tawh a ni.

Entirna dang chu accuracy drift a ni a, hei hian precision assembly, robot, motor, leh optical component te tan a tichhe hle tih a chiang hle.

Motor chhunga magnetic core awmna hmun, optical components alignment, leh structural parts dimension te hi a chhunga stress awm zawi zawiin a chhuah avangin long-term drift a tawk vek thei. Component-te chu a tir lamah chuan assembly laiin compliant ni mahse darkar za tam tak an thawh hnuah deviation an lantir a nih chuan, chutiang thil chu internal stress awmna atanga lo chhuak a ni fo thin.

Tin, fatigue life pawh a tlahniam bawk. Internal stress hian long-term average stress level a entir a, chu chuan a vaiin fatigue life curve a tihhniam a ni. Temperature cycling, humidity leh vibration te inzawmkhawm hian thil siamte chu initial testing paltlang mahse mass production-ah a hlawhchhamna dinhmun a thlen fo thin.

Chuvangin, internal stress hi secondary issue ni lovin bonding reliability atana fundamental prerequisite a ni zawk. Adhesion a awm theih leh theih loh chauh ni lovin, chu mi hnua bond chu eng chen nge a nghet reng tih pawh a hril bawk.

Internal stress hriatthiam tur chuan a bul tanna chu a hriatthiam hmasak a ngai a ni.

Adhesive curing laia internal stress hi a bulpui berah chuan strain chi hnih atanga lo chhuak a ni a, chungte chuan contract duhna an lantir a, mahse a takin an ti thei lo.

Category hmasa ber chu curing shrinkage a ni a, chemical shrinkage tia hriat bawk a ni.

Liquid monomer-ah chuan molecule te hian van der Waals force (weak interaction) hmangin contact an vawng reng thin. Molecules pahnih atom inkarah hian chemical bonds a awm lo va; an awm hnai mai a, an hlat zawng chu 0.3–0.4 nm vel a ni (chu chuan molecule pahnih van der Waals radii zatve a entir a ni).

Polymerization reaction chhung hian monomers inkarah covalent bonds a lo awm a. Entirnan C–C single bond hman tlanglawn ber chu la ila, a bond sei zawng hi 0.154 nm vel a ni. Chumi awmzia chu a tir lama 0.35 nm vel a loose distance-a inthen molecule pahnih chu tunah chuan 0.15 nm vel a sei covalent bond hmangin force-in an rawn inzawm khawm ta a ni-chu chuan intermolecular distance chu a chanve aia tam a tihhniam phah a ni. (Milem)

Macroscopic level-ah chuan chutiang molecular pair trillion tam tak a ruala inzawmkhawm chu volume tihtlem angin a lang chhuak a ni. Hei hi physical consequence a ni a, addition polymerization reaction engmah ah pawh pumpelh theih a ni lo.

Category pahnihna chu thermal mismatch stress a ni.

Adhesive tam tak chu a dam theih nan heating a ngai thin. Curing hnuah temperature sang atanga room temperature thlenga tihlum a nih chuan adhesive leh substrate te thermal expansion coefficient a inang lo.

Adhesive-a thermal expansion coefficient hi a tlangpuiin base materials metal, magnet, leh ceramics te aiin a sang zawk hle. Cooling lai hian adhesive chu a contract zual duh a, mahse base material chuan a free contraction a veng a, chu chuan adhesive layer chu a tikhawlo a, residual internal stress a siam bawk.

Hetah hian concept pawimawh ber chu gel point hi a ni.

Gel point hma hian adhesive chu a fluid reng a, a luang thei bawk. Hetih lai hian contraction a awm pawhin, chu material chuan chutiang deformation chu flow, reorganization leh filling hmangin a ti bo thei a, chu chuan internal stress pungkhawm chu a ti tlem thei a ni.

Gel point hnuah chuan thil awmdan a danglam ta a ni. Adhesive chhungah hian three-dimensional network a lo piang tan a, chu chu material chu liquid atanga solid state-ah a inthlak zauh zauh a ni. Hetiang dinhmunah hian adhesive layer chuan load-bearing capacity a nei a, a hnu lama shrinkage leh deformation thil thlengte chu "a hre reng" tan ta a ni.

Phên dangin sawi ila, gel point hnua contraction lo awm portion chu internal stress siamtu a ni tak zet a ni.

Hun a kal zel a, chu thil chu a nghet zual sauh a, a Tg chu a sang zel bawk. Tg hian tuna operating temperature a pelh chuan adhesive layer chu rubbery state atanga glassy state ah a inthlak thin.

Glass state a luh chuan adhesive layer modulus chu a pung chak hle a, chu chuan chain segment kal a ti harsa zual a; chuvângin, a hmaa chhuah theih stress ṭhenkhat chu chhuah a harsa zual sauh a ni.

Chuvangin, chhungril lama lungkhamna hi hetiang hian kan hrethiam mai thei:

Gel point hmain: stress thlen awlsam lovin contraction a awm thei.

Gel point hnuah: gel layer chuan network a siam tan a, a hnu lama shrinkage a awm loh nan.

Vitrification hnuah: material chu a rigid a, a molecular chain te chu a immobilized a, chu chuan stress release a ti harsa zual hle.

Kan hriat vek angin:

Stress=Modulus × Strain tih a ni

A tawp berah chuan chhungril lama stress ≈ effective modulus × (post-gelation curing shrinkage + thermal mismatch deformation) − relaxation chhuahna

Heat mismatch deformation hi hetiang hian hriatthiam theih a ni:

Thermal mismatch deformation ≈ (adhesive-a thermal expansion coefficient − substrate-a thermal expansion coefficient) × temperature danglamna tha tak

Gel point hnua contraction leh thermal mismatch lo awm, modulus sang zel hmanga tihpun, process chhunga relaxation hmanga chhuak portion minus chauh hian final net internal stress a siam a ni.

Hei hi internal stress zirchian a harsat chhan pawh a ni: instant khatah a lo chhuak nghal lo va, curing leh cooling process-ah a pung zauh zauh thin. Hetiang a nih chhung zawng hian shrinkage, temperature, modulus, leh material-in stress a chhuah theihna zawng zawng hi a inthlak danglam zel a ni.

Tunah chuan internal stress hi instant khatah a lo chhuak nghal lo va, curing leh cooling process-ah a pung zauh zauh zawk tih hriat lar tak a ni.

Hetah hian parameter tin hi a danglam reng a: contraction rate, temperature, modulus, leh material-in stress a chhuah theihna pawh a inang lo vek.

Chuvangin, internal stress characterization hi numerical value pakhat chauh a innghat thei lo va; zawhna pahnih chu a rualin a chhang tur a ni:

Pakhatnaah chuan, a tawpah engzat nge stress emaw deformation emaw a la awm?

Pahnihnaah chuan, engtin nge heng stress te hi curing process-ah hian a lo awm?

Test dan chungchang sawi dawn chuan a tlangpuiin chi hnih ah then theih a ni.

Category pakhatah chuan stress emaw deformation result direct measurement a awm a, a dang erawh chuan model dinna atan material intrinsic parameters a teh thung.

Category 1: Stress emaw deformation result emaw direct-a tehna

Hetiang approach hian adhesive a cured hnua structure-a deformation emaw residual stress emaw awm zat hriat chian a tum ber a ni.

Classical ber chu cantilever beam emaw bimaterial beam bending approach emaw a ni. Adhesive hi metal sheet te tak te, silicon wafer emaw substrate material dang emaw ah an hnawih thin a; curing laiin adhesive shrinkage hian substrate chu a bend tir thin. Curvature chu real time-a teh a, Stoney-a equation nena inmil method hmangin adhesive layer chhunga stress average chu chhut theih a ni. Hetiang approach hian intuitive leh well{3}}established a nihna hlawkna a pe a, curing time nena stress a danglam dan tarlanna curve te hmuh theih a ni.

Fiber Bragg grating (FBG) technique pawh a awm bawk. Gel layer chhunga optical fibers embed hian gel chhunga strain chu real time-in a teh theih a ni. Hetiang method hian surface deformation measurement chauh nena khaikhin chuan gel chhungril dinhmun dik zawk a pe a, mahse hei hian cost sang zawk leh operational complexity nasa zawk a keng tel a ni.

Distributed optical sensor hmanga composite laminate-a cure strain enfiahna (Image source)

Transparent adhesives tan chuan photoelasticity emaw birefringence method hmangin stress-induced birefringence hmanga stress distribution enfiah theih a ni bawk.

Tin, residual stress emaw indirect strain emaw tehna atan hian drilling, core sampling, X-ray diffraction (XRD), neutron scattering, leh Raman shift analysis te pawh hman theih a ni bawk.

Tunah hian biak theih reng e